1. Field of the Invention
The present invention relates to the use of communications networks and, in particular, to the use of integrated services digital networks (ISDN).
2. Background Information
It is often desirable to use high-bandwidth communications networks, such as ISDN, to communicate with specified end points. ISDN lines and services are provided by ISDN providers, such as telephone companies. In some present ISDN systems, such as North American ISDN, a user employs a service profile identifier (SPID) to establish an ISDN communications channel or circuit through a particular ISDN port over a particular physical ISDN line. The SPID identifies what types of communication and other services may be provided to the user over the particular ISDN line. The SPID may also be applied by the ISDN provider to a database that specifies the services allowed for a given user over a given ISDN line.
Thus, for a user of a particular ISDN line who has previously purchased a certain group of services from an ISDN service provider, a SPID is established ahead of time, and provided to the user, which allows usage of the ISDN line by the user in accordance with the permitted group of services. The SPID is typically a multi-digit number (for example, a ten to fifteen digit number) that is transmitted to the user once it is generated, for example by regular mail, after the user and ISDN provider agree to a particular group of ISDN services.
In ISDN, users have access to both a first-type channel which is a relatively low-bandwidth data channel (D channel), and one or more second-type or relatively high-bandwidth bearer channels (B channels). Both B and D channels are full duplex digital communication channels. A D channel is used to switch on and control the use of B channels. To access an ISDN connection or coupling, the D channel is used to establish at least one B channel. Another B channel may be added as desired for higher bandwidth signal throughput. For example, one B channel may be used for data communications and a second B channel may be used for voice communications.
When a user of an ISDN line wants to establish an ISDN coupling to a particular end point, such as an Internet service provider (ISP), a "set up" or "call request" message is transmitted over a D channel to the ISDN switching system of the central office system of the ISDN provider, which specifies the ISP which is the end point to be called and the type of ISDN coupling to be set up. The SPID is also transmitted to the ISDN provider during this set up process. The SPID may be used by the ISDN provider to access a database which specifies the services associated with the SPID and associated ISDN line. The ISDN provider is thus able to manage and control use of its ISDN lines, bill for usage, and the like.
If the ISDN provider approves the requested call to be placed and ISDN services requested, after using the supplied SPID to check permitted ISDN services in the database, the switching system transmits a message to the ISP notifying the ISP of the inbound call. If the ISP answers the inbound call, a B channel circuit mode connection or coupling is set up between the ISP and the user.
Unfortunately, a SPID that provides the desired level of services for a particular ISDN line is not always available. For example, users of ISDN are not always physically present at their own ISDN terminal, for which a SPID may already be set up. The user may be in an airport or hotel, and may desire to access the ISDN line of a public ISDN terminal for high-bandwidth communication purposes. Since it is not known which ISDN services a given user would like to use ahead of time, it is difficult to provide a fixed SPID at each ISDN terminal. Also, since each SPID is unique to a given ISDN terminal and line and the user does not know ahead of time which ISDN terminal he will use, it is difficult to provide a user ahead of time with a SPID for arbitrary ISDN terminals. Thus, currently it is difficult for a user to gain mobile access to an ISDN line.